The present invention concerns novel derivatives of thiadiazole compounds. More particularly, the new thiadiazoles are derived from 2,5-dimercapto-1,3,4-thiadiazole and maleic compounds. The invention further concerns improved lubricating compositions containing said reaction products.
Additives known as antiwear agents are employed to increase the load-carrying capacity of lubricants. The antiwear agents promote the formulation of a surface film and thereby prevent wear of the contacting surfaces.
During the course of use, lubricants are susceptible to deterioration due to oxidation. The oxidative process leads to the loss of lubricating properties and inadequate protection of the device to be lubricated. Antioxidants are added to inhibit the oxidative process. Thus, it is desirable that antiwear agents possess antioxidant properties.
The most commonly used additives to exhibit antiwear and antioxidant properties are zinc dihydrocarbylphosphorodithioates. However, due to stricter environmental controls, it is particularly desirable to reduce the phosphorus content in lubricants. There is a need to develop improved lubricating compositions that are environmentally sound.
It has been surprisingly discovered that the foregoing disadvantages of the prior art lubricants can be eliminated by replacing all or part of the phosphorus-containing additive with certain maleic derivatives of 2,5-dimercapto-1,3,4-thiadiazoles.
Known reaction products of a dispersant, 2,5-dimercapto-1,3,4-thiadiazole and maleic acid have been disclosed as extreme pressure agents and corrosion inhibitors in U.S. Pat. No. 4,140,643 to Davis.